Catelyn is portrayed by Northern Irish actress Michelle Fairley on the HBO series Game of Thrones.[1] American actress Jennifer Ehle was originally cast as Catelyn Stark and appeared in the unaired pilot, but left the series for family reasons before the first season began.[2][3] Fairley's portrayal of Catelyn has garnered critical acclaim, with many in particular praising her performance during the episode "The Rains of Castamere".[4] Due to this popularity, many fans were disappointed she did not appear in the series' fourth season, despite the character's resurrection in the novels.[5][6]

Catelyn Tully Stark is described as beautiful, with auburn hair, blue eyes, and long fingers, and dressed simply in the grey color of House Stark or the blue and red of her father’s House Tully. She is proud, strong, kind, and generous, has a strong grasp of politics, and is often governed by the desire to protect her children. Catelyn is usually in accord with her husband Eddard Stark, but resents his admission of his illegitimate son Jon Snow into their household.

After the royal party arrives at Winterfell, Catelyn receives a letter from her sister Lysa Arryn stating that the Lannisters had killed her husband Jon Arryn, the king's 'Hand' (second-in-command). King Robert Baratheon persuades Eddard to take his place. When her son Bran is injured and goes into a coma, she sits by his bed until they are attacked by an assassin who has come to kill Bran. Catelyn is wounded in the attack, and travels to King's Landing to warn Eddard after recovering. There, her childhood companion Petyr Baelish tells her that the dagger used in the attack belongs to Tyrion Lannister. On her way back to Winterfell, she takes Tyrion to her sister at the Eyrie for trial, where Tyrion escapes execution by demanding and winning a trial by combat. After the news of Eddard's execution by order of King Joffrey reaches Catelyn, she argues for peace, but is overruled by the newly crowned King Robb and his bannermen.

Catelyn advises against Robb's plan to send Eddard's former ward, Theon Greyjoy, to forge an alliance with Balon Greyjoy. Catelyn is sent by Robb to attempt an alliance with Renly Baratheon and his massive Reach-Stormlands host. Catelyn meets Renly at Bitterbridge and follows his host to the ancestral Baratheon seat of Storm's End, where she witnesses first the unsuccessful parley between Renly and his older brother and rival claimant Stannis, and then Renly's subsequent murder later that night by a shadow creature. Afterwards, Catelyn flees with Brienne of Tarth, one of Renly's kingsguard, to Riverrun. Upon hearing of her younger sons' supposed murder at the hands of Theon Greyjoy, Catelyn goes to confront the captive Jaime Lannister. Although the novel ends her storyline ambiguously, it is revealed at the beginning of the third novel that Catelyn set him free and asked Brienne to escort him to King's Landing in an attempt to exchange him for her daughters, who were still captives of Joffrey. This, however, causes problems for Robb and costs him an ally, House Karstark, which had held grudges against the Lannisters.

Catelyn's brother Edmure Tully places Catelyn under house arrest at Riverrun, but Robb pardons her after he announces his wedding to Jeyne Westerling, invalidating his marriage proposal to House Frey. Lord Walder Frey agrees to forgive Robb if Edmure marries his daughter Roslin, and Catelyn travels to the Frey seat of the Twins to attend the wedding with Robb and other northern lords. However, Walder Frey and his men take revenge on Robb for his slight on their house by slaughtering the northern host, an act of treachery that became known as the "Red Wedding". In an attempt to save her son's life, Catelyn takes Aegon Frey hostage and kills him when Roose Bolton kills Robb regardless, but she still has her throat slashed by Raymund Frey. Three days later, Catelyn is resurrected by Lord Beric Dondarrion, who sacrifices his life force to revive her. However, the period of time she spent deceased has caused Catelyn's body to decay; furthermore, upon her reanimation, she loses most of her previous personality, except for her hatred of House Frey. Catelyn then assumes command of Dondarrion's outlaw band, the Brotherhood Without Banners, and changes their aim to exterminating House Frey. Her uncompromising brutality earns her the moniker "Lady Stoneheart".

Stoneheart and the Brotherhood come across a small party led by Brienne, who informs Stoneheart that she is searching for Sansa at Jaime Lannister's request. Stoneheart names Brienne a traitor because she carries Oathkeeper, a Lannister sword that was forged from Ned Stark's Valyrian steel blade, Ice. Brienne swears that she is still faithful, but Stoneheart insists she must prove it by killing Jaime, whom she believes played a role in the Red Wedding. Brienne refuses, even when threatened with a hanging. Just before Brienne is to be hanged, she shouts out a word.

In January 2007 HBO secured the rights to adapt Martin's series for television.[7][8]Jennifer Ehle was originally cast as Catelyn Stark and filmed her scenes in the unaired pilot until she eventually left for family reasons.[2][3]Michelle Fairley was then cast in the role which she played for three seasons. Catelyn's storyline diverges from the book following the Red Wedding; as of the seventh season, no mention has been made of Lady Stoneheart, Ser Beric Dondarrion has reappeared as the leader of the Brotherhood, and the two associated POV characters, Brienne and Jaime, have both gone through the Riverlands without encountering her. It is widely assumed she has been cut from the television adaptation.

Michelle Fairley's performance has received critical acclaim. Time wrote about "The Rains of Castamere": "Michelle Fairley’s fantastic performance captures the horror, with the edge of desperation, anguish, and madness of a woman who has lost her sons (she believes all of them), lost her grandchild, may have lost her daughters, and for all she knows, is witnessing the extinction of the house she belongs to...".[9] The closing scene of "Cripples, Bastards, and Broken Things" was praised by HitFix's Alan Sepinwall, highlighting Michelle Fairley's acting as Catelyn gathers allies to arrest Tyrion.[10]